Electronic components/circuits are very important as the functioning of consumer electronics, industrial and household appliances depend on them. Various examples of electronic components are rectifiers, battery chargers, inverters, uni-directional or bi-directional converters, diodes, transistors, clippers, dampers, etc. Of these, rectifiers are widely used in the electronics industry and find a huge number of applications in our day-to-day life. The applications include deriving Direct Current (DC) power from an Alternating Current (AC) supply, power supplies, and detecting amplitude modulated radio signals.
Rectifiers are electronic components used for converting an Alternating Current (AC) into a Direct Current (DC). Rectifiers take the current that flows alternately in both directions and modifies it so that the output current flows only in one direction. The process of conversion of AC to DC is termed as rectification. Rectifiers are broadly classified as half-wave rectifier and full-wave rectifier.
In a half-wave rectifier, only one half of an AC wave, i.e. either the positive or the negative half is allowed to pass, while the other half is eliminated. The output of a half-wave rectifier can be achieved with a single diode connected in between a power supply and a load resistance or load reactance.
FIG. 1 shows a conventional half-wave rectifier circuit 100. FIG. 1 is shown to include an AC power supply 102, a diode 104, and a load 106. AC power supply 102 is connected to diode 104. Diode 104 is further connected to load 106, generating an output waveform. Load 106 can be a resistive load or a reactive load. Diode 104 is forward-biased and reverse-biased alternatively during every cycle of the AC wave. Further, diode 104 only passes one half of the AC wave during the forward-biased condition and blocks the other half of the AC wave during the reverse-biased condition. The output waveform at load 106 thus has a DC component.
Similar to the half-wave rectifier, a full-wave rectifier also produces DC output; however, it consists of two or more diodes connected to a single load resistance or reactance. Each diode supplies current to the load, in isolation from the other diode. Also, at least one of the diodes is always active during either the positive or negative cycle of an input AC wave. Therefore, the full-wave rectifier converts both polarities of the input AC wave to DC. Full-wave rectifiers are more efficient as compared to the half-wave rectifiers and have some fundamental advantages over the half-wave rectifiers. The output of a full-wave rectifier has much less ripple than the output of a half-wave rectifier and thus, produces a smoother output waveform.
Rectifiers are also commonly used as received signal strength indicators (RSSI). As the name suggests, RSSIs are used to measure the strength of an incoming signal. In general, a signal strength indicator circuit receives an input RF signal and produces an output, which is equivalent to the strength of the input signal. If the output voltage is high, then the signal strength is also high and vice-versa. An RSSI is commonly used in Automatic Gain Control (AGC) loops. Depending on the received signal power, the signal is amplified using an amplifier to boost the signal if it is too low or attenuated using an attenuator if it is too high. There are a number of consumer devices with inbuilt RSSI circuits, such as cell phones, wireless network adapters, and remote controls. Moreover, antennas contain RSSI circuits that help in aligning the antenna for maximum signal reception.
A number of Complementary metal-oxide-semiconductor (CMOS) solutions are available in the market that utilizes rectification techniques employed in RSSI implementations. However, such solutions require a lot of additions and subtractions to the current during the rectification process, which in turn requires very precise mathematics to be implemented. High precision further requires use of a long/large gate length to be utilized in such solutions. Typically, the gate length means the channel/region length representing the movement of the electrons and/or holes between two terminals formed inside the devices, for example, a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET). Typically, a MOSFET is employed in electronic circuits for the purpose of amplifying or switching electronic signals. Large gate length leads to large gate area, resulting in large capacitance, which in turn leads to poor frequency response. If the existing circuit designs have a small gate length; it becomes very difficult to achieve such precision, due to large variations in device characteristics in the process for minimal gate length devices. There are RSSI implementations for devices having a large gate length, thereby providing good matching of characteristics of various components in the circuit. However, such designs fail to work at very high frequencies. These designs perform badly as they can operate only at a limited frequency range.
In view of the aforesaid challenges, there exists a need for a circuit design that operates in a broad frequency spectrum and achieves a large dynamic range with the circuit exhibiting rectification as well as amplification characteristics. Moreover, the circuit design should be simple and the circuit should employ minimum gate length.